This brief aims to show the effects of threading edge dislocations on the dc and RF performance of GaN highelectron mobility transistor (HEMT) devices. A state-of-the-art high-frequency and high-power HEMT was investigated with our full-band cellular Monte Carlo (CMC) simulator, which includes the full details of the band structure and the phonon spectra. A complete characterization of the device has been performed using experimental data to calibrate the few adjustable parameters of the simulator. Thermal simulations were also carried out with commercial software in order to operate the corrections needed to model thermal effects. The approach of Weimann based on the results of Read, Bonch-Bruevich and Glasko, and Pödör was then used to model with our CMC code the dislocation effects on the transport properties of HEMT devices. Our simulations indicate that GaN HEMT performance exhibits a fairly large dependence on the density of thread dislocation defects. Furthermore, we show that a threshold concentration exists, above which a complete degradation of the device operation occurs.
In this work we propose a force-field scheme for the self-consistent particle-based simulation of electrolytic solutions. Within this approach, the electrostatic interactions are modeled with a particle-particle-particlemesh (P 3 M) algorithm, where the long-range components of the force are resolved in real space with an iterative multi-grid Poisson solver. Simulations are performed where the solute ions are treated as Brownian particles governed by the full Langevin equation, while the effects of the solvent are accounted for with the implicit solvent model. The main motivation of this work is to efficiently extend the modeling capability of the standard particlebased approaches to liquid systems characterized by a spatially inhomogeneous charge distribution and realistic, non-periodic boundary conditions. Examples of such systems are large polymer chains, biological membranes, and ion channels.
Results demonstrating the field effect modulation of ionic transport through an array of cylindrical nanopores fabricated in silicon-on-insulator substrates are presented. Pronounced modulation of the conductance is observed at low electrolyte concentrations when the electric double layers within the nanopores are overlapping. A numerical model based on Brownian dynamics reproduces the measured data.
We present a method for microfabricating apertures in a silicon substrate using well-known cleanroom technologies resulting in highly reproducible giga-seal resistance bilayer formations. Using a plasma etcher, 150μm apertures have been etched through a silicon wafer. Teflon™ has been chemically vapor deposited so that the surface resembles bulk Teflon and is hydrophobic. After fabrication, reproducible high resistance bilayers were formed and characteristic measurements of a self-inserted single OmpF porin ion channel protein were made.
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